Kinetic Theory - Result Question 25
25. One mole of an ideal diatomic gas undergoes a transition from $A$ to $B$ along a path $AB$ as shown in the figure.
The change in internal energy of the gas during the transition is:
(a) $-20 kJ$
(b) $20 J$
(c) $-12 kJ$
(d) $20 kJ$
[2015]
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Answer:
Correct Answer: 25. (a)
Solution:
- (a) Change in internal energy from $A \to B$
$\Delta U=\frac{f}{2} nR \Delta T=\frac{f}{2} nR(T_f-T_i)$
$=\frac{5}{2}{P_f V_f-P_i V_i}$
$=\frac{5}{2}{2 \times 10^{3} \times 6-5 \times 10^{3} \times 4}$
$=\frac{5}{2}{12-20} \times 10^{3} J=5 \times(-4) \times 10^{3} J$
$\Delta U=-20 KJ$
(As gas is diatomic $\therefore f=5$ )
